Ultra-sensitive electrochemical sensors based on self-assembled chelating dithiol on gold electrode for trace level detection of copper(II) ions

Humans are exposed to copper via contaminated drinking water/food and other environmental sources which pose an increasing threat to healthy functioning of life-sustaining metabolic activities and demands regular monitoring of copper content in the environment, i.e. soil and water. In the present work, chelating dithiol, bis (34(5-mercapto-1,3,4-thiadiazol-2-yecarbamoyephenyeterephthalate (BMTCPT) was synthesized and self-assembled on the surface of gold electrode which allows the formation of macrocycle capable of accommodating metal ions. Self-assembly of dithiol was confirmed by electrochemical techniques: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in two redox probes: anionic, [Fe(CN)(6)](3-/4-) and cationic, [Ru (NH3)(6)](2+/5+) and further, utilized as a platform for impedimetric sensing for Cu2+. EIS studies showed that AuBMTCPT electrode displayed a very sensitive and selective response towards Cu2+ in wider linear concentration range from 1.0 x 10(-12) M to 1.0 x 10(-5) M (r(2) = 0.990) at pH = 5 with lower detection limit of 9.7 x 10(-13) M. In addition, dithiol self-assembled gold nanoparticles (BMTCPT-AuNPs) were applied to construct a chemically modified carbon paste electrode (CPE) and subjected to potentiometric detection of Cu2+ which exhibited a Nernstian slope of 29.85 +/- 0.2 mV per decade in concentration range of 1.0 x 10(-9) M - 1.0 x 10(-4) M (r(2) = 0.999) with a detection limit of 8.91 x 10(-10) M.